Robert G. Natelson (The Independence Institute) has posted The Original Meaning Of ‘Emoluments’ in the Constitution on SSRN. Here is the abstract:
This Article explores the original meaning of the word “Emolument(s)” in the Constitution. It identifies four common definitions in founding-era political discourse. It places the constitutional use within its context as part of a larger reform movement in Britain and America and as driven by other historical events. The Article examines how the word was employed in contemporaneous reform measures, in official congressional and state documents, in the constitutional debates, and in the constitutional text.
The author concludes that the three appearances of “emoluments” in the Constitution had a common meaning, which was “compensation with financial value, received by reason of public employment.”
By the way, there is an excellent post by my colleague, John Mikhail, on this topic at Balkinization: A Note on the Original Meaning of "Emolument".